"First, Shanks says Vincennes and Indianapolis differed in many ways before 1964. For example, he says Vincennes observed DST in 1946 and from 1956 through 1963. I assume you merely copied Indianpolis's table to Vincennes for time stamps until now, which wouldn't be quite right." Correct. I bow to your superior research on that point. Second: "> In addition to the section above, the new zone will need to be added
to the zone.tab file. Vincennes' location is +384042-0873058.
My proposed patch had +384038-0873143 which is fairly close. (The LMT figures also diverged, presumably because of the coordinate difference.) My latitude and longitude are from Shanks." My figures come from the Census Bureau (with LMT computed from them, so that probably does explain the difference). "I'm not sure how Shanks (or anyone else) decides where Vincennes "is", given that one arc second of latitude is only 31 meters or so." The Census Bureau indicates that its figures are based on the approximate geographic center of the area, provided that point is actually in the area.